Messages in this thread | | | Date | Thu, 30 Nov 2017 15:24:21 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] riscv/ftrace: Add basic support |
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On Thu, 30 Nov 2017 16:53:35 +0800 Alan Kao <nonerkao@gmail.com> wrote:
> This patch contains basic ftrace support for RV64I platform. > Specifically, function tracer (HAVE_FUNCTION_TRACER), function graph > tracer (HAVE_FUNCTION_GRAPH_TRACER), and a frame pointer test > (HAVE_FUNCTION_GRAPH_FP_TEST) are implemented following the > instructions in Documentation/trace/ftrace-design.txt.
Hmm, that document is somewhat out of date. Hopefully it was good enough. I'm going to need some time to update it.
> > Note that the functions in both ftrace.c and setup.c should not be > hooked with the compiler's -pg option: to prevent infinite self- > referencing for the former, and to ignore early setup stuff for the latter.
I'm curious to what is in setup.c that ftrace uses.
> > Signed-off-by: Alan Kao <alankao@andestech.com> > --- > arch/riscv/Kconfig | 8 +++ > arch/riscv/include/asm/Kbuild | 1 - > arch/riscv/include/asm/ftrace.h | 23 +++++++ > arch/riscv/kernel/Makefile | 7 ++ > arch/riscv/kernel/ftrace.c | 56 ++++++++++++++++ > arch/riscv/kernel/mcount.S | 139 ++++++++++++++++++++++++++++++++++++++++ > 6 files changed, 233 insertions(+), 1 deletion(-) > create mode 100644 arch/riscv/include/asm/ftrace.h > create mode 100644 arch/riscv/kernel/ftrace.c > create mode 100644 arch/riscv/kernel/mcount.S > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 2e15e85c8f7e..07c3df0919b7 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -60,6 +60,12 @@ config PAGE_OFFSET > config STACKTRACE_SUPPORT > def_bool y > > +config TRACE_IRQFLAGS_SUPPORT > + def_bool y > + > +config LOCKDEP_SUPPORT > + def_bool y
Hmm, not sure the above is needed for function tracing.
> + > config RWSEM_GENERIC_SPINLOCK > def_bool y > > @@ -112,6 +118,8 @@ config ARCH_RV64I > bool "RV64I" > select CPU_SUPPORTS_64BIT_KERNEL > select 64BIT > + select HAVE_FUNCTION_TRACER > + select HAVE_FUNCTION_GRAPH_TRACER > > endchoice > > diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild > index 18158be62a2b..680301bfbc4b 100644 > --- a/arch/riscv/include/asm/Kbuild > +++ b/arch/riscv/include/asm/Kbuild > @@ -12,7 +12,6 @@ generic-y += errno.h > generic-y += exec.h > generic-y += fb.h > generic-y += fcntl.h > -generic-y += ftrace.h > generic-y += futex.h > generic-y += hardirq.h > generic-y += hash.h > diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h > new file mode 100644 > index 000000000000..38beadb07ad5 > --- /dev/null > +++ b/arch/riscv/include/asm/ftrace.h > @@ -0,0 +1,23 @@ > +/* > + * Copyright (C) 2017 Andes Technology Corporation > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License > + * along with this program. If not, see <http://www.gnu.org/licenses/>. > + */ > + > +/* > + * The graph frame test is not possible if CONFIG_FRAME_POINTER is not enabled. > + * Check arch/riscv/kernel/mcount.S for detail. > + */ > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && defined(CONFIG_FRAME_POINTER) > +#define HAVE_FUNCTION_GRAPH_FP_TEST > +#endif > diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile > index ab8baf7bd142..15941f3b8363 100644 > --- a/arch/riscv/kernel/Makefile > +++ b/arch/riscv/kernel/Makefile > @@ -2,6 +2,11 @@ > # Makefile for the RISC-V Linux kernel > # > > +#ifdef CONFIG_FTRACE > +CFLAGS_REMOVE_ftrace.o = -pg > +CFLAGS_REMOVE_setup.o = -pg > +#endif > + > extra-y += head.o > extra-y += vmlinux.lds > > @@ -29,5 +34,7 @@ CFLAGS_setup.o := -mcmodel=medany > obj-$(CONFIG_SMP) += smpboot.o > obj-$(CONFIG_SMP) += smp.o > obj-$(CONFIG_MODULES) += module.o > +obj-$(CONFIG_FUNCTION_TRACER) += mcount.o > +obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o > > clean: > diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c > new file mode 100644 > index 000000000000..e425c8f3f1cd > --- /dev/null > +++ b/arch/riscv/kernel/ftrace.c > @@ -0,0 +1,56 @@ > +/* > + * arch/riscv/kernel/ftrace.c > + * > + * Copyright (C) 2013 Linaro Limited > + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> > + * Copyright (C) 2017 Andes Technology Corporation > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License > + * along with this program. If not, see <http://www.gnu.org/licenses/>. > + */ > + > +#include <linux/ftrace.h> > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
This file only gets compiled when that config is set. This #ifdef is somewhat redundant.
> +/* > + * Most of this file is copied from arm64. > + */ > +void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, > + unsigned long frame_pointer) > +{ > + unsigned long return_hooker = (unsigned long)&return_to_handler; > + unsigned long old; > + struct ftrace_graph_ent trace; > + int err; > + > + if (unlikely(atomic_read(¤t->tracing_graph_pause))) > + return; > + > + /* > + * We don't suffer access faults, so no extra fault-recovery assembly > + * is needed here. > + */ > + old = *parent; > + > + trace.func = self_addr; > + trace.depth = current->curr_ret_stack + 1; > + > + if (!ftrace_graph_entry(&trace)) > + return; > + > + err = ftrace_push_return_trace(old, self_addr, &trace.depth, > + frame_pointer, NULL); > + if (err == -EBUSY) > + return; > + *parent = return_hooker; > +} > +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S > new file mode 100644 > index 000000000000..5307358219bf > --- /dev/null > +++ b/arch/riscv/kernel/mcount.S > @@ -0,0 +1,139 @@ > +/* > + * Copyright (C) 2017 Andes Technology Corporation > + * Author: Alan Kao <alankao@andestech.com> > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License > + * along with this program. If not, see <http://www.gnu.org/licenses/>. > + */ > +#include <linux/init.h> > +#include <linux/linkage.h> > +#include <asm/asm.h> > +#include <asm/csr.h> > +#include <asm/unistd.h> > +#include <asm/thread_info.h> > +#include <asm/asm-offsets.h> > +#include <asm-generic/export.h> > +#include <asm/ftrace.h> > + > + .text > + > + .macro SAVE_ABI_STATE > + addi sp, sp, -16 > + sd s0, 0(sp) > + sd ra, 8(sp) > + addi s0, sp, 16 > + .endm > + > + /* > + * The call to ftrace_return_to_handler would overwrite the return > + * register if a0 was not saved. > + */ > + .macro SAVE_RET_ABI_STATE > + addi sp, sp, -32 > + sd s0, 16(sp) > + sd ra, 24(sp) > + sd a0, 8(sp) > + addi s0, sp, 32 > + .endm > + > + .macro STORE_ABI_STATE > + ld ra, 8(sp) > + ld s0, 0(sp) > + addi sp, sp, 16 > + .endm > + > + .macro STORE_RET_ABI_STATE > + ld ra, 24(sp) > + ld s0, 16(sp) > + ld a0, 8(sp) > + addi sp, sp, 32 > + .endm > + > +ENTRY(ftrace_stub) > + ret > +ENDPROC(ftrace_stub) > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > +ENTRY(return_to_handler) > +/* > + * On implementing the frame point test, the ideal way is to compare the > + * s0 (frame pointer, if enabled) on entry and the sp (stack pointer) on return. > + * However, the psABI of variable-length-argument functions does not allow this. > + * > + * So alternatively we check the *old* frame pointer position, that is, the > + * value stored in -16(s0) on entry, and the s0 on return. > + */ > +#ifdef HAVE_FUNCTION_GRAPH_FP_TEST > + mv t6, s0 > +#endif > + SAVE_RET_ABI_STATE > +#ifdef HAVE_FUNCTION_GRAPH_FP_TEST > + mv a0, t6 > +#endif > + la t0, ftrace_return_to_handler > + jalr t0 > + mv a1, a0 > + STORE_RET_ABI_STATE > + jr a1 > +ENDPROC(return_to_handler) > +EXPORT_SYMBOL(return_to_handler) > +#endif > + > +ENTRY(_mcount) > + la t4, ftrace_stub > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > + la t0, ftrace_graph_return > + ld t1, 0(t0) > + bne t1, t4, do_ftrace_graph_caller
If function graph is enabled, you jump straight to the graph tracer, but never return back to here?
> + > + la t3, ftrace_graph_entry > + ld t2, 0(t3) > + la t6, ftrace_graph_entry_stub > + bne t2, t6, do_ftrace_graph_caller > +#endif > + la t3, ftrace_trace_function > + ld t5, 0(t3) > + bne t5, t4, do_trace > + ret > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > +/* > + * A pseudo representation for the function graph tracer: > + * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller) > + */ > +do_ftrace_graph_caller: > + addi a0, s0, -8 > + mv a1, ra > +#ifdef HAVE_FUNCTION_GRAPH_FP_TEST > + ld a2, -16(s0) > +#endif > + SAVE_ABI_STATE > + la t0, prepare_ftrace_return > + jalr t0 > + STORE_ABI_STATE
I'm guessing you don't support function tracer and function graph tracer running at the same time?
-- Steve
> + ret > +#endif > + > +/* > + * A pseudo representation for the function tracer: > + * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller) > + */ > +do_trace: > + ld a1, -8(s0) > + mv a0, ra > + > + SAVE_ABI_STATE > + jalr t5 > + STORE_ABI_STATE > + ret > +ENDPROC(_mcount) > +EXPORT_SYMBOL(_mcount)
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